Baghouse with double pass traveling purge head

ABSTRACT

A cleaning purge head for a baghouse traveling centrally of the clean air plenum to isolate and back flush with high pressure air successive compartments of filter bags arranged in two parallel banks of filters. Through a depressible seal, the purge head communicates with a pressure chamber supplying cleaning air. A cam activated valve regulates the bursts of cleaning air supplied to successive filter bag compartments as a delivery conduit registers therewith such that the purge head alternates in cleaning the two banks of filters on successive passes through the baghouse.

BACKGROUND AND SUMMARY OF THE INVENTION

This application is a continuation-in-part application of my copendingapplication Ser. No. 806,188 filed June 13, 1977, now U.S. Pat. No.4,097,254.

This invention relates to dust control equipment and, more particularly,to a compartmentalized baghouse equipped with a traveling purge head tosuccessively isolate and clean compartments of filter bags.

Continuous emphasis on environmental quality has resulted inincreasingly strenuous regulatory controls on industrial emissions. Onetechnique which has proven highly efficient in controlling air pollutionhas been the separation of undesirable particulate matter from a gasstream by fabric filtration.

Such filtration is carried out in dust collection equipment known in thetrade as a "baghouse" which operates on the same general principle as anordinary household vacuum cleaner, except on a much larger scale.Basically, the baghouse includes a sheet metal housing divided into twochambers, referred to as plenums, by a tube sheet having a plurality ofvertically suspended fabric tubes or bags in which cylindrical wirecages are inserted for skeletal support. A particle-laden gas stream,induced by the action of a fan, flows into the lower chamber (dirty airplenum) wherein dust accumulates on the cloth bags as the gas passesthrough the fabric into the upper chamber (clean air plenum) and out theexhaust. Continuous operation of the unit causes a cake of dust to buildup on the outside of the bags which, unless removed, will reduce andeventually stop the flow of gas through the filters.

Several methods have been devised to remove the dust cake from the bags.One cleaning technique to which this invention particularly relatesprovides for a cleaning or purge head which reciprocally travels thelength of the baghouse at the side thereof while successively isolatingsections of the clean air plenum and causing relatively high pressureair to back flush through the isolated section, thereby dislodging thedust cake from the filter bags. My earlier U.S. Pat. No. 3,482,378issued Dec. 9, 1969 and entitled "Traveling Purge Head Dust Filter"discloses a baghouse possessing such characteristics. In theaforementioned patent, a plurality of baffles divide the clean airplenum into successive sections, each communicating with an exhaustduct. For each section so defined, filtered gas normally flows throughthe bags and into the clean air compartment thereabove and out thecommon exhaust. The purge head traveling along the side of the clean airplenum periodically and successively covers the mouth of eachcompartment and discharges high pressure air therein to clean the filterbags associated with that particular compartment.

The adaptability of these principles to baghouses of increasing size issomewhat limited. It is not always physically feasible, much lesseconomically practical, to simply build a larger and longer baghouse inorder to achieve increased capacity. Floor space within the plant posesa constraint on the baghouse dimensions. Furthermore, a larger baghousewould require, a priori, enlarged support facilities such as thecleaning system which represents a significant capital investment andincreases operational costs. Accordingly, there is a need in theindustry for adapting the beneficial qualities of a traveling purge headto baghouses of a much larger capacity than those heretofore employingthis cleaning technique while at the same time minimizing the investmentand operational costs occasioned by the cleaning system. The primaryobject of this invention is to fulfill this need.

More specifically, an object of the invention is to provide a baghousewith a traveling purge head to function centrally of the clean airplenum as opposed to traveling along the side of the clean air plenum ashas been the practice with equipment of this type.

In conjunction with the foregoing object, it is equally important toprovide a baghouse of increased capacity without a correspondingincrease in the size of the purge air system. Significant investment andoperational savings are realized by employing a purge air systemvirtually half as large as that which would be necessary for prior artdesigns wherein the purge head delivers its bursts of cleaning air fromone side of the baghouse.

A myriad of problems are presented however, in contemplating the changeof location of the purge head from operating alongside the clean airplenum to operating centrally of the clean air plenum. Provision must ofcourse be made to provide a high pressure cleaning air source to thepurge head. Furthermore, provision must be made for a valve mechanism tonot only control the intermittent purging of successive compartments ofthe clean air plenum, but also to control the direction of the cleaningpulse whether it is to the right or the left of the direction of travelof the purge head.

Consequently, a further object of this invention is to provide a valvemechanism for a traveling purge head to intermittently control the flowof high pressure air to an isolated compartment of the clean air plenum,and to also control the direction of the cleaning discharge as the purgehead moves centrally through the clean air plenum. A corollary object isto provide a valve mechanism of the character described which is simplein construction and economical in manufacture. Ease of maintenance isalso a significant feature of the valve.

Yet another object of the invention is to provide a high pressure airconduit centrally of the clean air plenum wherein the traveling purgehead is in communication with the pressure duct and is equipped withunique seal means to permit movement of the purge head along thepressure duct while at the same time continuously supplying pressurizedcleaning air to the purge head.

Other and further objects of the invention, together with the featuresof novelty appurtenant thereto, will appear in the course of thefollowing description of the drawings.

DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, which form a part of the specification andare to be read in conjunction therewith, and in which like referencenumerals are employed to indicate like parts in the various views:

FIG. 1 is a perspective view of a baghouse constructed in accordancewith a preferred embodiment of the invention with parts thereof brokenaway to better illustrate the details of construction;

FIG. 2 is a top plan view of the baghouse with portions of the topaccess door broken away to illustrate the construction of the clean airplenum;

FIG. 3 is a side elevational view taken along line 3--3 of FIG. 2 in thedirection of the arrows;

FIG. 4 is an end elevational view taken along line 4--4 of FIG. 3 in thedirection of the arrows;

FIG. 5 is an enlarged top plan view of the cleaning head valve takenalong line 5--5 of FIG. 4 in the direction of the arrows;

FIG. 6 is an enlarged sectional plan view taken through the cleaninghead valve along line 6--6 of FIG. 4 in the direction of the arrows;

FIG. 7 is a fragementary elevational view taken along line 7--7 of FIG.6 in the direction of the arrows;

FIG. 8 is an enlarged end view, partly fragmentary, showing a portion ofthe drive assembly taken along line 8--8 of FIG. 3 in the direction ofthe arrows; and

FIG. 9 is an enlarged elevational view, partly fragmentary, of the lowerportion of the cleaning head taken along line 9--9 of FIG. 4 in thedirection of the arrows.

Referring to the drawings in greater detail, the baghouse generallycomprises a sheet metal housing 10 interiorly divided by horizontallymounted tube sheets 11. A plurality of filter bags 12, each containing acylindrical cage 13 for skeletal support, are received within holes inthe tube sheets 11. Employing standard terminology, the region of thehousing in which the filter bags 12 are suspended is referred to as thedirty air plenum and is fitted with a process gas inlet port 10a, whilethe region of the housing above the mouths of the filter bags 12 isreferred to as the clean air plenum. The roof of the baghouse comprisesa plurality of removable access panels 14 supported on a strut network15. The ends of the clean air plenum may be conventionally flanged withductwork 16 used to discharge clean air or connected to a prime moverfan (not shown) for drawing process gas through the baghouse.

The lower section of the housing is characteristically hopper-shaped toreceive dust cake dislodged from the bags during the cleaning operation.In the bottom of the hopper may be located an auger or other suitableequipment for removal of the collected dust cake.

As shown in FIG. 2, the filter bags 12 are arranged in two longitudinalbanks with the center of the clean air plenum being void of filtrationfunction. Each bank of tubes is sectioned by vertical baffles 17 whichextend between the tube sheet 11 and top access panels 14 and the sidewall of the housing 10 to create a plurality of plenum compartmentsabove each bank of filter tubes. The flanged mouth 18 of eachcompartment opens to the central portion of the clean air plenum andslopes outwardly from bottom to top.

Centrally disposed in the clean air plenum is a purge head to be laterdescribed in greater detail, being generally designated by the numeral20. The purge head 20 rides in a trough 21 defined by a floor panel 21aand side walls 21b running longitudinally and centrally through thebaghouse. At opposite ends of the trough 21 are mounted sprockets 22 and23 around which is engaged a continuous drive chain 24. The sprocket 22at one end of the chain 24 is carried on a rotatable shaft 25 receivedby pillow blocks 26 mounted on a support pad 27 and secured to theductwork 16 at the end of one bank of tubes. Likewise, at the oppositeend of the chain 24 as illustrated in FIG. 2, the sprocket wheel 23 iscarried on a rotatable shaft 28 received by pillow blocks 29 on anunderlying support pad 30. The opposite end of the shaft 28 is fittedwith a suitable drive sprocket 31 coupled to a motor 32 by a continuouschain 33. Operation of the motor 32 thus causes continuous rotation ofthe drive chain 24 engaged around the sprockets 22 and 23 as indicated.

The purge head 20 includes a box-like carriage 34 having a longitudinalopening 34a through which passes the drive chain 24 which rides on idlersprocket 35 mounted on one side wall of the opening 34a. Mounted atopposite ends of the carriage are sheaves 36 around which is engaged acontinuous chain or cable 37. As best shown in FIG. 8 the carriage cable37 is coupled to the drive chain 24 by means of a pin 38 which causesthe drive chain 24 to pull the purge head 20, via the carriage cable 37,through the center of the clean air plenum with the open bottom of thecarriage 34 sliding on the floor panel 21a of the trough 21.

Underlying the central trough 21 of the clean air plenum is a pressureconduit 40 as shown in FIGS. 3 and 4 which extends the length of thebaghouse. One end of the conduit is fitted with a blower 41 forsupplying high pressure cleaning air. The floor panel 21a of the troughseparating the trough 21 from the pressure conduit 40 includes anelongate slot 21c therethrough to provide communication with thepressure conduit 40. At the opposite ends of the conduit 40 is secured aflexible belt 42 at the upper end of the end closure panels 40a. Whencompressed air is supplied to the chamber 40, the belt 42 billows up toseal the elongate slot 21c as shown in the various views.

As best illustrated in FIGS. 3, 4 and 9, a vertical fin 43 is secured tothe bottom of the carriage and penetrates the slot in the floor panel ofthe trough 21. Within the pressure conduit 40, the end edges of the fintaper inwardly and mounted along the periphery of the fin are aplurality of rollers 44 which engage the flexible belt 42. Secured tothe fin 43 and projecting outwardly therefrom a distance at least equalto half the width of the flexible belt 42 are a plurality of supportrods 45. On the outer ends of the rods 45 are a pair of angles 46 spacedapart slightly greater than the width of the flexible belt 42 tounderlie the floor panel 21a. Secured to the outer ends of the angles 46are a pair of retaining rods 47 over which is passed the flexible belt42. Thus, when the conduit 40 is not pressurized with cleaning air, theretaining rods 47 prevent the belt from falling away from the contour ofthe fin 43. It should be apparent at this point that the structure thusfar described, when the pressure conduit 40 is supplied with positiveair pressure, admits air flow through the elongate slot 21c onlyadjacent the vertical fin as it depresses the belt 42 away from the slot21c, while the belt creates a seal over the rest of the slot 21c.

Secured to the outer ends of the carriage 34 are stub rods 48substantially the same size as the width of the slot 21c to keep thecarriage in tracking alignment with the slot.

Mounted atop the carriage 34 is a substantially square valve housing 50.Secured to each side of the housing 50 and projecting outwardly towardeach bank of filter tubes is an air delivery conduit 51 having aninclined flanged mouth 51a to complementarily mate with the mouths 18 ofthe compartments. The mouth 51a of each conduit 51 is trimmed with aseal plate 52 to slidingly seal against the mouth 18 of eachcompartment.

Within the valve housing 50 is received a cylindrical valve 53 having anopen bottom which swivels on the top plate of the carriage housing 34,having holes 34b therethrough to establish communication between theinterior chamber of the carriage and the interior of the valve. Thevalve 53 also includes an elongate vertical slot 53a in the cylindricalsurface thereof. A vertical axle 54 extends centrally through the valve53 being secured at the lower end thereof to cross braces 55 from thecylindrical valve wall and being secured at the upper end to the topcircular plate 53b of the valve. The lower end of the axle 54 projectsfrom the cross braces 55 notably through the top plate of the carriage34. At its upper end, the axle 54 extends from the top of the valve 53through an opening in the mounting plate 56 bolted to the top plate ofthe valve housing 50 and which carries a bearing 57 to rotatably receivethe axle 54. As best illustrated in FIG. 5, a cross bar 58 is pinnedintermediate the ends thereof to the valve axle 54. One end of the crossbar is equipped with a cam roller 59 and the opposite end is connectedto a tension spring 60. The opposite end of the tension spring 60 isadjustably held in the slot 61a of the bracket 61 secured to the top ofone of the delivery conduits 51 projecting from the side of the valvehousing 50. The spring tension is so adjusted as to maintain the valve53 in a position where the cross member 58 is in alignment with thespring 60 as shown in the broken line view of FIG. 5.

As best shown in FIGS. 6 and 7, each corner of the valve housing 50 isfitted with an upright channel assembly 62. Each channel assembly 62holds a sealing strip 63 which is biased to engagement with thecylindrical surface of the valve 53 by means of adjustable lugs 64 whichpenetrate the corner of the housing 50 and are received by threadablenuts 65 secured to the housing 50.

Secured centrally of the clean air plenum to the roof supporting strutnetwork 15 is a cam track 66 having mounted thereon a plurality of camlobes 67. The lobes 67 are located at a sufficient height to strike thecam roller 59 on the cross member 58 of the valve 53 as the purge head20 travels the length of the baghouse.

In operation, the baghouse constructed in accordance with the foregoingprinciples functions in the following manner. Process gas laden withparticulate matter, induced by a fan either upstream or downstream ofthe baghouse, flows through the inlet port 10a into the dirty airplenum. The gas then passes through the filter bags 12 leaving theparticulate matter deposited thereon and flows upwardly through thecenter of the cages 13 supporting the bags 12 to the plurality ofcompartments in the clean air plenum. The clean air then flows out ofthe mouths 18 of the compartments into the central region of the cleanair plenum and out the exhaust ductwork 16.

Operation of the drive chain 24, coupled to the carriage 34 by theconnecting pin 38 attached to the carriage cable 37 pulls the purge head20 through the clean air plenum. At the end of the tube banks, furtherprogress of the purge head 20 is halted while the connecting pin 38travels from the leading end of the carriage 34 around the drivesprocket 22 or 23 to the opposite end of the carriage 34, such movementof the connecting pin 38 being accomplished by rotation of the carriagecable 37 upon the carriage sheaves 36. When the connecting pin 38reaches the far end of the carriage 34, the purge head 20 is then pulledin the opposite direction by the drive chain 24.

As the purge head 20 travels through the clean air plenum, operation ofthe cleaning air supply blower 41 causes the flexible belt 42 to sealagainst the elongate slot 21c in the floor 21a of the trough. Aspreviously indicated, the vertical fin 43 depresses the flexible belt 42beneath the carriage 34 and admits compressed air into the interiorchamber of the carriage 34 and upwardly into the cylindrical valve 53through ports 34b. As the purge head 20 moves along, the flexible belt42 disposed under the vertical fin 43 is simply depressed by theplurality of roller members 44.

As the purge head 20 is traveling between compartments, the dischargeslot 53a in the cylindrical valve 53 is oriented along the longitudinalaxis of the baghouse. The position of the cross bar 58, controllingrotation of the cylindrical valve 53 is as shown in the broken line viewof FIG. 5. When, on the other hand, the air delivery conduit 51registers with the mouth 18 of a compartment, the cam roller 59 on thecross bar 58 strikes a cam lobe 67 causing elongate slot 53a of thevalve 53 to rotate 90° to orient with the delivery conduit 51. Thus, onecompartment registering with the purge head 20 is momentarily isolatedwhile cleaning air is discharged to the compartment. The cleaning airflows down through the bags 12 associated with that compartment causingthem to billow and dislodge particulate matter collected on the bags 12.The dislodged particulate matter than falls into the hopper-shapedbottom of the dirty air plenum for removal in conventional manner. Asthe purge head 20 passes the cleaned compartment, the cam roller 59disengages the cam lobe 67 and the tension spring 60 causes the valve 53to snap back to a closed position to shut off air flow to a deliveryconduit 51, until the purge head 20 registers with the next successivecompartment where the previously described action is repeated. Thus, onecomplete bank of tubes 12 is successively cleaned compartment aftercompartment. Upon reaching the end of the bank of tubes, the purge head20 reverses and travels in the opposite direction. On this subsequentpass through the clean air plenum, the cam roller 59 strikes the camlobes 67 from the opposite direction causing the valve 53 to rotate 90°from the closed position to clean the second bank of tubes. The actionof the valve 53 is thus reversed on each subsequent pass of the purgehead 20 through the clean air plenum so that the baghouse experiences acomplete cleaning cycle of all bags with the up and down travel of thepurge head 20.

It should be understood that the cam lobes are a simple and convenientmechanical method by which to control operation of valve 53. The generalintent, however, is to cause the valve to open when the purge headregisters with a compartment in the clean air plenum and to close whenthe purge head travels between compartments. As those knowledgeable invalve control art will easily recognize, the on-off valve operation anddirection of discharge could likewise be achieved by severalconventional techniques such as timing control circuitry or tripswitches to cause a valve to deliver the required burst of cleaning air.Such is envisioned as being within the scope of the invention.

From the foregoing it will be seen that this invention is one welladapted to attain all ends and objects hereinabove set forth togetherwith the other advantages which are obvious and which are inherent tothe structure.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is comtemplated by and is within the scope of theclaims.

Since many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim:
 1. Apparatus for separatingparticulate matter from a gas stream, said apparatus comprising:ahousing; a substantially horizontal partition disposed interiorally ofsaid housing, thereby defining a first chamber above said partition anda second chamber beneath said partition, said partition having aplurality of openings therethrough; an inlet conduit connected to saidsecond chamber for directing a particulate laden gas stream into saidsecond chamber; an outlet conduit communicating with said first chamberto exhaust gas therefrom; a plurality of filters disposed in said secondchamber and having open ends secured to said openings through saidpartition, said filters being arranged in two parallel, spaced apartbanks; a plurality of vertical dividers arranged in said first chamberabove said two banks of filters to thereby define compartments havingmouths opening centrally of said first chamber; a movable cleaning headdisposed within said first chamber between said banks of filters andhaving an air delivery conduit adapted to matingly register with andseal against said compartment mouths; drive means coupled to saidcleaning head to move said head longitudinally forward and backwardwithin said first chamber between said banks of filters; pressurized airsupply means connected to said cleaning head to supply pressurizedcleaning air thereto; valve means mounted on said cleaning head tonormally restrict flow of cleaning air from said delivery conduit andintermittently operable to transmit to burst of cleaning air throughsaid delivery conduit; and valve discharge control means positioned andarranged with respect to said valve means to cause said valve means totransmit a burst of cleaning air through said delivery conduit each timesaid delivery conduit aligns with a compartment mouth of one bank offilters as said cleaning head travels through said first chamber in onedirection and to cause said valve means to transmit a burst of cleaningair through said delivery conduit each time said delivery conduit alignswith a compartment mouth of the second bank of filters as said cleaninghead travels through said first chamber in the opposite direction. 2.The apparatus as in claim 1, said drive means comprising:a pair ofsprockets mounted within said first chamber at opposite ends of saidfilter banks; an endless drive chain engaging said sprockets; powermeans coupled to one said sprocket to continuously drive said endlessdrive chain around said sprockets; and reverse motion coupling meansmounted on said cleaning head and connected to said endless drive chainto reciprocally move said cleaning head longitudinally forward andbackward within said first chamber between said banks of filters.
 3. Theapparatus as in claim 2, said reverse motion coupling means comprising:apair of sheaves mounted on said cleaning head; an endless flexible loopengaging said sheaves in parallel, but spaced apart relationship to saidendless drive chain; and a coupler linking said flexible loop to saiddrive chain; whereby said drive chain, acting through said loop andcoupler, pulls said cleaning head in one direction to the end of saidfilter banks where said cleaning head momentarily stops as said couplertravels with said drive chain around one sprocket and said loop travelsaround said sheaves until said coupler travels approximately one halfthe length of said loop where said drive chain pulls said cleaning headin the opposite direction between said filter banks.
 4. The apparatus asin claim 1, said pressurized air supply means comprising:a conduitdisposed between said filter banks and having an elongate slotcommunicating with said first chamber; blower means connected to saidconduit to supply cleaning air thereto; and a flexible belt mountedwithin said conduit in alignment with said slot to mate with and sealsaid slot when said blower means supplies cleaning air to said conduit;and said cleaning head including a belt depressing member penetratingsaid slot to hold said flexible belt adjacent said cleaning head awayfrom sealing engagment with said slot to admit cleaning air to saidcleaning head.
 5. The apparatus as in claim 4, said cleaning headfurther including belt retaining members connected to said depressingmember to hold said flexible belt in contact with said depressing memberwhen said blower means fails to supply cleaning air to said conduit. 6.The apparatus as in claim 4 including rollers mounted on said beltdepressing member to rollably engage said flexible belt as said cleaninghead travels between said filter banks.
 7. The apparatus as in claim 1,said valve means comprising:a valve housing mounted on said cleaninghead and connected to said air delivery conduit; a cylindrical valvebody disposed within said valve housing for pivotal movement therein andhaving one closed end and one substantially open end communicating withthe pressurized cleaning air supplied to said cleaning head and furtherhaving a discharge disposed through the cylindrical valve body; and saidvalve discharge control means normally biasing said valve body to aclosed position to restrict air flow to said air delivery conduit, butoperable to rotate said valve body within said valve housing to registersaid discharge with said air delivery conduit and to admit cleaning airthereto when said delivery conduit aligns with a compartment mouthduring travel of said cleaning head between said filter banks.
 8. Theapparatus as in claim 7, said valve means further including a pluralityof elongate sealing strips adjustably mounted within said valve housingto bear against said cylindrical valve body.